Nonuniform displacements of copper atoms in dilute interstitial Cu-C solid solutions

Strong deformational interaction in interstitial solid solutions leads to considerable nonuniform static displacements of the solvent atoms. Knowledge of values of these displacements allows us to predict the the tendencies to the concentrational polymorphic transformation in the alloys with interstices. Displacements show how the lattice "prepares" itself for the phase transition when the concentration of alloying atoms is changed. Nonuniform displacements of copper atoms in dilute interstitial Cu-C solid solution with fcc structure are calculated in the framework of the microscopic phenomenological theory of interstitial solid solutions. We calculate quasielastic Kanzaki forces and nonuniform static displacements of of copper atoms in the copper-rich region of the phase diagram. These results are compared with first-principles density functional calculations which have been made in the embedded cluster scheme. Bonding structure and cohesive energy were analyzed to extract details of the impurity-metal interaction, and to map a portion of the potential energy surface. Calculations show that off-center, nonuniform displacements are energetically favored.